Starting an internal combustion engine in low ambient air temperatures, for example below 0° C., is often difficult without the use of starting aids, such as glow plugs. When cold air is drawn into the cylinder of a cold engine, piston velocity needs to be high in order to raise the temperature at top dead centre of the piston cycle and help the fuel in the cylinder to ignite. This is particularly true for diesel engines. However, the piston velocity when starting the engine is dependent on the starter motor alone, which is in turn powered by batteries. Consequently, the starter motor often does not produce a high enough piston velocity to start the engine and the battery may be drained before the engine is able to fire.
Thus, in low ambient air temperatures it is sometimes not possible to start an internal combustion engine, and even when the engine will start, it may take a considerable amount of time to warm up the engine to operating temperatures.
Similar problems may occur at high altitude where the concentration of oxygen in the air is lower than at sea level, and where the ambient air temperature is also low the problems may be even more severe.
The problem may be even more exacerbated if there are any parasitic loads on the engine. For example, if a diesel engine is fitted in a machine, such as a construction or agricultural type machine, the machine may make use of an implement or boom that uses hydraulics to function. Hydraulics require a hydraulic pump to be running, which adds a parasitic load on the engine as the engine starts.
U.S. Pat. No. 7,360,361 describes an engine arrangement in which an electrically assisted turbocharger is fitted to the engine. Soon after a cold start, or other low idle conditions, the electric induction motor of the electrically assisted turbocharger is turned on by a controller if the exhaust gas output from the engine is insufficient to cause the turbocharger to supply adequate amounts of fresh air to the air intake manifold of the engine. As the engine increases its speed and produces more exhaust gas to drive the turbocharger, the controller responsively reduces power to the induction motor.
After turning on the induction motor of the electrically assisted turbocharger, it may take some time for the intake manifold air pressure to increase to a level at which combustion within the cylinders is made easier. Therefore, at least the first few combustion cycles after starting the engine will not experience any improvement in the ease of combustion. Consequently, whilst the arrangement suggested in U.S. Pat. No. 7,360,361 might help to bring the engine speed up more quickly, it does not assist in the actual starting of the engine.